Drum-type mining machines have come into extensive use. Briefly, such machines generally comprise a self-propelled vehicle having a centrally located conveyor means for removing the material being mined. At the forward end of the machine, one or more movable beams support a horizontally oriented drum. The drum bears a plurality of cutting tools. Frequently, the cutting tools are oriented on the drum in a pattern comprising two oppositely oriented helices which are directed toward the center of the drum. This aids in conducting the cut material toward the center of the machine and the conveyor which forms a part of it.
Through an appropriate drive mechanism and gearing, in association with the beam or beams, the drum is caused to rotate about its axis to produce the cutting action. In the usual practice, the machine is brought to the face of the material being cut and the drum is sumped into the face at the top thereof. Thereafter, through the agency of the beam or beams, the rotating drum is caused to move downwardly, making a complete vertical cut at the face of the material. This procedure is then repeated and the mine entry is thereby advanced.
At the position or positions where the drum is supported on one or more of the beams, the drum cannot carry cutting tools. Therefore, one or more trim chains are required to fill in those portions of the drum not otherwise provided with cutting tools. By virtue of the construction of such mining machines, it often develops that the trim chains have to be of considerable width. As a consequence, such trim chains usually carry a plurality of cutting tools located in patterns of staggered rows extending the width of the chain, so that the chain will make a full width cut.
The earlier of such trim chains were comprised of a plurality of chain blocks joined together by two or more connecting links. Each block was as wide as the chain width required and each carried at least one cutting tool in a predetermined position along the chain width. Thus, for each cutting tool position there had to be a separate type of chain block configured to mount the cutting tool in that position.
These earlier trim chains performed fairly well in the field but they required the mine owner to carry a large inventory of different and expensive wide chain blocks for purposes of replacement and repair. In addition, since some mine owners could have several different drum-type mining machines, each using trim chains of different widths, he would then be required to maintain an inventory of sets of wide chain blocks for each type of machine.
Improvement on these wide block trim chains, however, has been made. Such improvement has generally taken the form of a chain construction in which the trim chain is comprised of a plurality of interdigitated link elements, some of which are simply connecting links, and some of which are bit carrying links. Spacer means may be substituted for selected ones of the connecting links or of the bit carrying links and as a consequence the term "link element" is generally construed as encompassing connecting links, bit carrying links and spacer means.
Improved trim chains of the type just mentioned are shown in U.S. Pat. Nos. 3,679,265 and 3,888,133. These improved trim chains are made up of a plurality of transverse rows of link elements with any desired arrangement of connecting links and bit carrying links. The number of elements in each row may be varied so as to provide a trim chain of any desired width. As indicated, the ends of the lik elements of adjacent rows are interdigitated and held together by connecting pins of appropriate length passing through coaxial perforations in the interdigitated link element ends. These chains may be driven by sprocket means engaging the ends of select link elements at selected positions along the width of the chain, or by engaging the ends of the connecting pins.
The aforementioned patents make other teachings which may also be incorporated in the chain of the instant invention. Thus, for example, it is taught that spacer elements may be substituted for a connecting link, for purposes of economy. Not only may the bits be located in various patterns on the selected link elements but also the bit may be skewed; that is, selected bits may be in line with the axis of the chain and the direction of chain movement, i.e., the cutting direction, while other bits may be oblique thereto. These patents also teach means for retaining the connecting pins in the chain and for protecting them from wear. It is also taught in these patents that chains of this general type may be modified to serve as a tread for a self-propelled vehicle and it is indicated that when so used all of the link elements comprising the chain may be identical, or the chain may be comprised of a plurality of standard link elements and a plurality of modified link elements to produce various desired results. These features, and others, may be incorporated in the instant invention.